This paper presents an innovation of language games for practicing English vocabulary mastery. The main focus of the study was to investigate the development of Monolary (The given name toward the game) while specifically, it focused on: (1) investigating the media and games used in teaching vocabulary; (2) investigating the development of Monolary; and (3) investigating how could Monolary be used as a media or game in practicing students' vocabulary mastery. The participants were five elementary English teachers and 132 students of five elementary schools in Bali. The instruments used were questionnaires, observation sheets, and interview guide. The results show that (1) teachers did not have any media and games to support vocabulary teaching and (2) the development of Monolary was based on vocabulary learning theories which could be used as media of practicing as well as assessing vocabulary mastery of elementary schools' students. From the aforementioned results, it can be concluded that teachers need media and games to support vocabulary teaching and Monolary could be one solution.